(a) Field of the Invention
The present invention relates to a method and apparatus for canceling interference. Particularly, the present invention relates to a method and apparatus for canceling interference that is adaptive to environments in an orthogonal frequency division multiplexing (OFDM) wireless transmission system.
(b) Description of the Related Art
In an orthogonal frequency division multiplexing (OFDM) wireless transmission system, when a frequency reuse factor is 1, interference coming from downstream transmission signals due to transmission signals from a base station of a neighbor cell generally causes performance degradation of the system. An apparatus for canceling interference provides smooth handover even when the magnitude of interference is greater than the magnitude of a desired signal in the edge of the cell.
Generally, various types of schemes can be used for interference cancellation. An interference cancellation scheme adopts a plurality of antennas at a receiver and estimates the same number of independent channels as the number of receiving antennas and an interference channel from the result that a signal transmitted via a single transmit antenna is received at different receiving antennas, thereby removing the interference in the received signal. In this instance, a pilot signal or a preamble corresponding to a known signal pattern between a transmitter and the receiver is used for estimation of the signal and the interference channel. The interference cancellation performance is determined according to a scheme of disposing the preamble or the pilot signal, and estimating the channel and the interference channel using the same.
Among various interference cancellation schemes, a maximal ratio combining (MRC) scheme regards interference as noise and then increases a signal-to-noise ratio (SNR), instead of estimating the interference channel.
When the receiver uses a single antenna, a least squares (LS) scheme, among the interference cancellation schemes, regards as if iteratively received MAP data is received via the same subcarrier and different antennas, based on the fact that the MAP data of an Institute of Electrical and Electronics Engineers (IEEE) 802.16e frame is iteratively transmitted over different subcarriers or time. Next, the LS scheme estimates a signal and an interference channel to cancel the interference using the estimation result.
However, since the MRC scheme and the LS scheme cancel the interference using a single scheme, the performance for interference cancellation may be different depending on the number of interferences and the magnitude thereof. Accordingly, it may be difficult to expect optimal interference cancellation using a single interference cancellation unit in real environments.